Credit

Caption

Slinky toy. View of a slinky toy moving down stairs. The slinky is a spring of metal which can move down stairs or ramps when pushed. As the top coil is pushed over the edge of the stair, the spring stretches, and pulls the rest of the slinky behind it. When the end of the slinky touches the lower stair, that end stops, and the rest of the slinky catches up. The momentum of this downward and forward movement means that the rear end overshoots the new base of the slinky, however, and starts a new cycle of movement by falling onto the next stair down. The potential energy in the spring is converted into kinetic energy during this motion.